Inductance



NOV. 23, 1954 O CLARK E L 2,695,387

INDUCTANCE Filed Nov. 8, 1950 l N V E N TO RS. Mao/v 0. CA mew Gsoegs le IWgHTMAM ATTORNEY United States Patent Ofifice 2,695,387 Patented Nov. 23, 1954 INDUCTANCE Nelson 0. Clark, Winthrop, and George R. Wightman, Fairhaven, Mass, assignors to Eastern Electric, Inc., New Bedford, Mass.

Application November 8, 1950, Serial No. 194,650

1 Claim. (Cl. 336-197) This invention relates generally to ballasts or ballast elements for gaseous electric discharge devices, and especially to the method of producing such ballasts and to the structure completed by following that method.

Ballasts or inductances for use with electrical devices are generally well known, and while the present invention deals with a ballast structure primarily designed for use with fluorescent lamps or the like, the principle of the structure and the method of producing it may find application in connection with many other electric devices for different uses.

It is one of the objects of this invention to produce inexpensively and eficiently an inductance structure which possesses all the advantages of similar, heretofore used devices, but wherein the manufacture of its components and their assembly are so simplified that the device may be produced in large volumes at a relatively small cost, and wherein the uniformity of the finished product can be readily maintained in quantitative manufacture.

Another object of this invention is the method of simultaneously securing and locating an inductance coil and its core within a pole piece without the use of riveting or the employment of auxiliary attaching elements, such as bolts, pins and the like.

Another object of this invention is the method of producing a ballast for fluorescent lamps and the like, which consists of bifurcating the two ends of a metal bar, then shaping the bar to form a U-shaped yoke so that the slots of the bifurcated ends become aligned with one another, inserting into the slotted ends of the yoke the projecting ends of a core which extends from an inductance coil so that the core ends pass into the bottoms of the slots, and thereupon forcing the termini of the slotted yoke ends against one another to impinge upon the core ends and to hold the core immovable, thereby locating not only the core but also the coil within the yo e.

A further object of this invention is the provision of a ballast element structure composed of an inductance coil,

a core passing through the coil and provided at its ends with recesses and end flanges, and which recessed core ends are held within the slotted ends of a substantially U-shaped yoke, and the termini of which slotted ends are compressed against the recessed portions of the core to hold both the core and the coil in fixed position with respect to the yoke.

The foregoing and numerous other objects and important advantages of this invention will become more fully apparent from the ensuing description in conjunction with the accompanying drawings, wherein:

Fig. 1 is a perspective view of a typical ballast structure constructed in accordance with the present method;

Fig. 2 is an elevation of an inductance coil, partly in section;

Fig. 3 is a perspective view of a pole piece constructed in accordance with the present invention; and

Fig. 4 is a perspective view of a core, also constructed in accordance with the present invention.

In these figures, numeral denotes an inductance coil provided with a hollow dielectric support 11, in the form of a tube, the ends 12 of which are preferably rolled outwardly into flanges for engaging and holding in place a pair of disc-shaped insulating end members 13, between which latter the winding of coil 10 is held in place.

As may be readily observed from Fig. 2, inductance coil 10, due to its central support 11 and end pieces 13 held by the support, forms a rigid structure. Fitting snugly into coil support 11 is a magnetic core 14 comprising a cylinder 15, the ends of which are recessed at 16 to form end flanges 17, the diameter of which latter is preferably smaller than that of cylinder 15.

Coil 10 is held by way or" core 14 in a mounting 18, which comprises a magnetic metal bar, the ends 19 of which are bifurcated by providing therein slots 20 while the bar is in its originally flat shape. Slots 20 are preferably uniform in width and depth. Following the slotting operation, the bar is shaped into a U-shaped yoke, as indicated in Fig. 3, by bending its bifurcated ends 19 along two parallel areas 21. Bifurcated ends 1% are uniform in length and the bottoms 22 of slots 20 and their parallel faces are in alignment with one another. The width of the slots, the thickness of the yoke material and the curvature of slot bottoms 22 substantially correspond to the respective dimensions and shapes of recessed portion 16 of core 14. It is to be noted that core 14, including its recessed and flanged ends, is longer than the height of coil 10 so that when the core is inserted into the coil, recessed portion 16 and its flanges 17 extend beyond flanged ends 12 of support 11.

The method of uniting the three elements of the ballast include the following steps: First, the placement of core 14 into hollow support 11 of coil 10 so that the ends of the core will extend the same distance beyond flanges 12 of the support; second, inserting the coil with the core thus positioned therein into mounting 18 so that recessed portions 16 of the core pass into slots 20 and engage bottoms 22 of the slots; third, while holding the core in that position Within the mounting, compressing the termini 23 and 23 and 24 and 24 of the upper and lower bifurcated ends of the yoke toward one another so that they impinge upon recessed portions 16 of the core and force them tightly against bottoms 22 of the slots and thereby hold not only the core but also coil 10 in fixed, immovable position relative to mounting 18.

Core 14 is preferably made of relay or any other suitable iron, and recesses 16 and flanges 17 may be produced thereon by any suitable known method. It is of course obvious that core 14 may be fabricated from comminuted powdered iron, which is molded to its desired form and sintered. Mounting or U-shaped yoke 18 is preferably produced from strip iron cut to size, slotted and bent.

The fabrication of inductance coils is well known and need not be specified, however it is preferred that the construction of the coil illustrated in Fig. 2 is adhered to, since its tubular support 11 with its flanged ends 12 will effectively resist deformation and will prevent the deflection of bifurcated ends 19 of the mounting.

The simplicity of the union of the three ballast elements and the method employed for uniting them avoids the usual riveting operation necessary to affix the core to the mounting and obviates the employment, in lieu of the riveting operation, of auxiliary fastening means such as screws, bolts, pins, etc. The only tool for locating and attaching the coil and the core in the mounting is an appliance for squeezing the termini 23 and 23' and 24 and 24 against each other so that the core is firmly held.

While in the foregoing a specific structure and a specific method are described in the production of a ballast element, it is obvious that both the method as well as the structural features of the invention may be subject to changes and modifications in the course of employment of the invention in different fields, such changes and modifications being deemed to reside within the broad scope and spirit thereof.

What is claimed as new is:

In a choke construction for use as a ballast element with gaseous electric discharge devices, an inductance coil comprising a winding of insulated wire mounted upon an insulating, hollow support, a pair of insulating end members associated with the ends of the support, the winding being disposed between said end members, a cylindrical magnetic core within the hollow support, the ends of the core having annular recesses to reduce the core body and to form end flanges, a substan- 3 tially U-shaped magnetic yoke having bent-in ends parallel to and aligned with one another, slots with rounded bottoms in these yoke ends dividing the latter into prongs, said prongs passing into said core recesses so that the rounded slot bottoms grip the reduced core body portions, the ends of the prongs being bent toward one another and fixedly holding the core, and thus the inductance coil and the, yoke against displacement.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 357,337 Rosenblatt Feb. 8, 1887 1,123,107 Darr Dec. 29, 1914 Number Name Date 1,627,765 Bates May 10, 1927 2,459,023 Gilman Jan. 11, 1949 2,513,965 Pettit July 4, 1950 2,595,562 Becker May 6, 1952 FOREIGN PATENTS Number Country Date 171,867 Great'Britain Dec. 1, 1921 16 582,960 Great Britain Dec. 3, 1946 OTHER REFERENCES Article: Experimental Arc Furnace Melts Everything, 1 p. 80Popu1ar Science Monthly, May 1933. 

